The present invention relates to compositions based on coal-tar oil for the protective treatment of wood. It furthermore relates to a process for the protective treatment of wood using the compositions according to the invention.
The use of coal-tar oil for protecting wood against rot and attack by insects has been known since the middle of the 19th century and is still customarily employed for preserving masts, fences, beams etc. Even early on, attempts were made to use coal-tar oil in the form of emulsions in water or aqueous protective salt solutions (zinc salts, copper salts). However, these use forms did not give the desired results, and most tar oils were still used undiluted. In addition, attempts were made to improve the unsatisfactory stability of coal-tar oil emulsions by xe2x80x9chomogenizationxe2x80x9d (analogously to the process used for milk) or by treatment with specifically adapted dispersing apparatus (for example ULTRA-TURRAX(copyright)) and diverse additives (AT-PS-86,925, EP-A-0 227 430). These processes involve expensive equipment and consume a lot of energy. More recently, the application of coal-tar oil emulsions in water attracted renewed interest, in particular since in this manner it is possible to partially eliminate or reduce some disadvantages of the undiluted coal-tar oil, such as, for example, the unpleasant odour, the tendency to sweat and the sticky surface of the treated woods (U.S. Pat. No. 5,098,472).
This known process has the disadvantage that the emulsions are relatively unstable and that, owing to the emulsion, the effective proportion of coal-tar is reduced by the proportion of water and the emulsifier(s), so that the amount that is applied has to be increased to ensure effective and long-lasting protection.
Accordingly, it was an object of the present invention to eliminate or reduce the disadvantages of the known preparation processes and applications of tar oil emulsions.
According to the invention, this object is achieved by the compositions described below and pressure treating wood with a composition of the present invention.
Surprisingly, it has been found that, by using biocidally active quaternary ammonium compounds, if appropriate together with polar solvents, such as, for example, glycol derivatives, it is possible to prepare stable emulsions and microemulsions of coal-tar oil in water by simple stirring without any special equipment requirements. Not only does the biocidal action of the quaternary ammonium compounds compensate for the fact that the tar oil is diluted, but it has additionally been foundxe2x80x94contrary to expectationsxe2x80x94that the depth of penetration and the activity spectrum considerably exceeds those of the pure undiluted tar oil.
The compositions according to the invention comprise at least the following components:
a) 5-90 parts, preferably 10-90 parts, of coal-tar oil
b) 2-20 parts of a biocidally active quaternary ammonium compound
c) 10-90 parts of water.
Here and below, all amounts are stated in parts by mass.
Suitable biocidally active quaternary ammonium compounds are, for example:
Nxe2x80x94C8-20-alkyl-N,N-dimethyl-N-benzylammonium chloride, bromide or iodide*) 
N,N-di-C6-20-alkyl-N,N-dimethylammonium chloride, bromide or iodide*) 
Nxe2x80x94C6-20-alkyl salts*) of pyridine, quinoline, etc.
Nxe2x80x94C6-20-alkyl-N,N,N-trimethylammonium chloride, bromide or iodide*) 
N,N-di-C6-20-alkyl-N-methyl-N-poly(ethoxy)ammonium salts*) 
*) Instead of the halides, it is also possible for the salts of other inorganic acids or organic carboxylic acids to be present, for example acetate, propionate, sulphate, etc.
It has been found, for example, that an emulsion comprising only 30% of tar oil, about 10% of a cationic ammonium compound, about 5% of auxiliary and 55% of water was at least twice as effective against wood-destroying fungi as undiluted pure coal-tar oil.
With the aid of these compositions, it is possible to utilize the excellent activity of coal-tar oil, supported by long-term experience, and at the same time to reduce considerably the disadvantages of odour, of sweating at high ambient temperatures, of elutability and of the oily sticky surface of the wood.
Simultaneously, better, i.e. more uniform and deeper, distribution of the protective composition in the wood is achieved andxe2x80x94this appears to be particularly advantageousxe2x80x94the wood can have a higher moisture content than would be possible if pure tar oil was used. Thus, the time and energy for drying the raw wood, for example beams and masts, can be reduced considerably.
A further advantage of the compositions according to the invention consists in the fact that they can be processed at normal ambient temperatures, in contrast to pure tar oil. That is to say that pure tar oil, owing to its viscosity and flow behaviour, can only be processed at temperatures of about 100xc2x0 C., which is associated with a high energy input. Moreover, this property of tar oil stands in the way of deep penetration and optimum distribution in the wood.
The intense odour of coal-tar oil is caused, in particular, by bi- and tricyclic aromatic compounds, for example naphthalene and alkylnaphthalenes. Only some of these can be removed by distillation since, if they are removed completely, a tar oil is formed which has a viscosity which is too high and not even manageable at 100-120xc2x0 C. Because of the way in which they are prepared, the compositions according to the invention permit the use even of tar oils of relatively high viscosity which, accordingly, are highly deodorized, which facilitates the use of coal-tar oil even in sensitive areas, for example beams for underground rails, or makes this use possible in the first place.
Preferably, the compositions according to the invention additionally comprise up to 20 parts of a polyglycol compound to improve (storage) stability. These include, for example, polyethylene glycols and polypropylene glycols, and their alkyl and aryl ethers and esters.
Particular preference is given to polyethylene glycol compounds such as, for example, polyethylene glycol, to ethoxylated phenols and to diethylene glycol monobutyl ethers.
In addition to the formulation components already mentioned, the compositions according to the invention may comprise, for example, the following substances:
resins, binders, polymers
waxes
dyes
pigments
antioxidants
odour-masking substances
markers (tracers)
They preferably comprise one or more components from the group of the resins, binders, waxes, dyes and pigments.
Particularly preferred binders are alkyd resins and similar resins based on natural oils, such as linseed oil or soya oil, in particular those which are water-soluble or water-dilutable owing to reaction with ethylene oxide or propylene oxide.
To widen the activity spectrum, the compositions according to the invention preferably additionally comprise an effective amount of one or more insecticides, fungicides, algicides or bacteriocides.
They may comprise, for example, one or more of the following active compounds:
Amphoteric surfactants having biocidal action
Methyl benzimidazol-2-ylcarbamate
1,2-Benzisothiazol-3-one
Biguanides having biocidal action
Organic and inorganic boron compounds
xcex1-tert-Butyl-xcex1-(p-chlorophenethyl)-1H-1,2,4-triazol-1-ethanol
2-sec-Butylphenyl N-methylcarbamate
(xc2x1)-cis-4-[3-(tert-Butylphenyl)-2-methylpropyl]-2,6-dimethylmorpholine
5-Chloro-2-methyl-4-isothiazolin-3-one
2-(4-Chlorophenyl)-3-cyclopropyl-1-(1H-1,2,4-triazol-1-yl)butan-2-ol
1-(6-Chloro-3-pyridinyl)methyl-4,5-dihydro-N-nitro-1H-imidazol-2-amine
Chlorohexidine and its salts
Chlorinated phenols, for example tetra- and penta-chlorophenol
Chloronitrobenzene derivatives
1-[4-(2-Chloro-xcex1,xcex1,xcex1-trifluoro-p-tolyloxy)-2-fluorophenyl]-3-(2,6-difluorobenzoyl)urea
1-(4-Chlorophenyl)-3-(2,6-difluorobenzoyl)urea
xcex1-[2-(4-Chlorophenyl)ethyl]-xcex1-(1,1-dimethylethyl)-1H-1,2,4-triazol-1-ethanol
Cyano(4-fluoro-3-phenoxyphenyl)methyl 3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropanecarboxylate
(RS)-xcex1-Cyano-3-phenoxybenzyl-(RS)-2-(4-chlorophenyl)-3-methylbutyrate
xcex1-Cyano-3-phenoxybenzyl isopropyl-2,4-dichlorophenylacetate
N-Cyclohexyl-N-methoxy-2,5-dimethylfuran-3-carboxamide Di(guanidinooctyl)amine
3-(2,2-Dibromovinyl-2,2-dimethyl)-xcex1-(cyano-m-phenoxy-benzyl-1R,3R)cyclopropanecarboxylate
1-[2-(2,4-Dichlorophenyl)-1,3-dioxolan-2-ylmethyl]-1H-1,2,4-triazole
1-[2-(2,4-Dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl-methyl]-1H-1,2,4-triazole
3-Phenoxybenzyl (+)-3-(2,2-dichlorovinyl-2,2-dimethyl)-cyclopropane-1-carboxylate
xcex1-Cyano-3,3-phenoxybenzyl 3-(2,2-dichlorovinyl-2,2-dimethyl)cyclopropane-1-carboxylate
O,O-Diethyl-O-(xcex1-cyanobenzylideneamino) thiophosphate
O,O-Diethyl-O-3,5,6-trichloro-2-pyridyl thionophosphate
O,O-Diethyldithiophosphoryl-6-chlorobenzoxazolone
5,6-Dihydro-2-methyl-1,4-oxathiine-3-carboxanilide
N,N-Dimethyl-Nxe2x80x2-phenyl-(Nxe2x80x2-fluoromethylthio)sulphamide
N,N-Dimethyl-Nxe2x80x2-tolyl-(Nxe2x80x2-fluoromethylthio)sulphamide
O,O-Dimethyl-S-(2-methylamino-2-oxoethyl) dithiophosphate
O,O-Dimethyl-S-(N-phthalimido)methyl dithiophosphate
3,5-Dimethyltetrahydro-1,3,5-thiadiazin-2-thione
Dimethylalkylamine salts
Dithiocarbamates, metal and amine salts
Ethyl 2-(4-phenoxyphenoxy)ethylcarbamate
2-(2-Furanyl)-1H-benzimidazole
Halogenated acetic acids and their amides and esters
6,7,8,9,10-Hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2,3,4-benzodioxothiepine 3-oxide
Hexachlorocyclohexane
8-Hydroxyquinoline and its halogenated derivatives
2-Iodobenzanilide
3-Iodo-3-propinyl butylcarbamate
Copper 8-oxyquinoline
1-Naphthyl N-methylcarbamate
2-Methyl-4-isothiazolin-3-one
Methylene bisthiocyanate
Nitroalkanols having biocidal action
N-Nitroso-N-cyclohexylhydroxylamine and its salts
N-Nitroso-N-phenylhydroxylamine and its salts
Norbornene dimethanohexachlorocyclosulphite
2-N-Octyl-4-isothiazolin-3-one
Organotin compounds, for example tributyltin oxide and tributyltin benzoate
Phenylphenols
2-Isopropoxyphenyl N-methylcarbamate
N-Propyl-N-[2-(2,4,6-trichlorophenoxy)ethyl]imidazole-1-carboxamide
Pyridine-2-thiol 1-oxide and its salts
Salicylanilide and its halogenated derivatives
(4-Ethoxyphenyl)[3-(4-fluoro-3-phenoxyphenyl)propyl]-(dimethyl)silane
N-(1,1,2,2-Tetrachloroethylthio)-3,6,7,8-tetrahydrophthalimide
Tetrachloroisophthalonitrile
2-(Thiazol-4-yl)benzimidazole
2-Thiocyanomethylthiobenzothiazole
1-(1,2,4-Triazol-1-yl)-1-(4-chlorophenoxy)-3,3-dimethylbutan-2-ol
1-(1,2,4-Triazol-1-yl)-1-(4-chlorophenoxy)-3,3-dimethylbutan-2-one
N-Trichloromethylthio-3,6,7,8-tetrahydrophthalimide
N-Trichloromethylthiophthalimide
N-Tridecyl-2,6-dimethylmorpholine
By addition of binders such as, for example, drying alkyd resins, acrylates or other polymers, it is possible to improve the surfaces of the treated woods mechanically and optically, and at the same time to reduce the mobility (leaching and bleeding) of the coal-tar oil even further. The systems according to the invention can furthermore, in contrast to coal-tar oil on its own, be modified by addition of dyes or pigments, such that it is possible to stain the woods treated. By addition of waxes, it is possible to achieve matting of the surfaces of the woods treated, in combination with a strong water-repelling effect which reduces the uptake of liquid water without obstructing moisture exchange via the vapour phase.
The preparations according to the invention are prepared, for example, as follows:
(I) 5-90 parts of coal-tar oil, for example WEI type C, are initially charged and, if appropriate at slightly elevated temperature (about 50xc2x0 C.), admixed with
(II) 2-20 parts of cationic surfactant, for example N,N-didecyl-N-methyl-N-poly-(ethoxy)ammonium propionate, and the mixture is stirred until homogeneity is achieved;
(III) 0-20 parts of glycol derivative, for example diethylene glycol monobutyl ether, are then added and the mixture is stirred until homogeneity is achieved,
(IV) 0-20 parts of stabilizer/solubilizer, for example p-nonylphenol ethoxylate (EO=10-14), are then added and the mixture is once more stirred until homogeneity is achieved, and the batch is cooled. After cooling,
(V) 10-90 parts of water are added and the mixture is stirred until a homogeneous emulsion has formed.
In this preparation process, stable, milky (opaque) or clear low-viscosity mixtures are-formed which can be introduced with good penetration into the wood using the boiler pressure method (use of reduced pressure and superatmospheric pressure), without raising the temperature. Depending on the proportion of the formulation components I, II and V, the total amount that has to be introduced for a comprehensive protection of the wood is 20-80 kg/m3 of wood.
The compositions according to the invention are preferably applied in vacuum boiler pressure units such that the compositions are introduced into the wood to be protected using differences in pressure. The process steps include a pre-vacuum phase, a flood phase during which the vacuum is maintained, and a pressure phase. If appropriate, the process is concluded by applying a final vacuum. The amount of the protective composition introduced is controlled by weighing. In the case of woods or wood species which soak easily, it is possible to increase the water content in the compositions even more, compared with the examples.
The impregnation is preferably carried out without heat input, i.e. approximately at ambient temperature.
If required, the water which is introduced into the wood together with the compositions can be removed by treatment with heat. If the preparations additionally comprise polymers which are curable at elevated temperatures, it is possible to treat the wood with hot steam. This steam treatment then results in a rediffusion and more even distribution of the compositions, combined with a more effective fixing. Polyethylene glycols, which are an optional constituent of the preparations, impart dimension-stabilizing properties to the preparations, combined with a significantly reduced tendency of the wood thus treated to crack.
Altogether, the compositions according to the invention have the following advantages compared with coal-tar oil:
1. high stability of the emulsions,
2. use at normal ambient temperature is possible,
3. good distribution of the protective composition even in woods with an average moisture content,
4. strongly reduced odour of the woods treated,
5. no annoying tar oil enrichments on the treated wood,
6. strongly reduced xe2x80x9cbleedingxe2x80x9d of the treated wood at hot temperatures,
7. the surface structure and the grain remain visible,
8. only slight discoloration of the surface,
9. compatibility with customary varnishes and clearcoats,
10. considerably enhanced activity in spite of a lower content of coal-tar oil in the preparations,
11. option to stain the treated woods,
12. less leaching of the treated woods, and consequently no relevant local environmental stress,
13. low toxicity compared with pure coal-tar oil,
14. less cracking when drying the treated wood,
15. option of using strongly deodorized, highly viscous tar oils.